Yesterday I changed the icons of my Cinnamon setup, to Moka. I didn’t install it through AUR though, I downloaded the .zip from GitHub and placed it in ~/.icons folder. All went well but I have found that in Nemo the right click menu has a HUGE icon for open as root.

Any suggestions on how to change it to some other icon (or no icon at all)?

~/.icons is no longer an officially supported location for icons. This means that apps won’t necessarily check for icons at that location. You should install the icon theme directory to /usr/share/icons.

You can go into theme settings. At the bottom of the main page there is an options section. Disable show icons in menu. This doesn’t correct the icon size issue, just disables them in the menu. Really no need for them in the menu anyway.